Noted one of a few cases where we do something immediately that could more

Noted one of a few cases where we do something immediately that could more
efficiently be postponed, quite easily---and which GLUT promises *is* to
be postponed.  (It is unlikely that the difference will break any apps, but
postponing should be easy...)

No real change, just a comment in the code.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@341 7f0cb862-5218-0410-a997-914c9d46530a